The invention relates to an optical measurement device for an electrical appliance having at least one electrical conductor that is pressed into a slot, which has two slot side walls, in a base body. In particular, the invention relates to an optical measurement device for an electrical appliance that is used in the field of electrical power generation and distribution, such as an electrical generator or an electrical transformer.
Such an electrical appliance, which is also referred to as power equipment, represents a very expensive and long-term investment. Its failure not only endangers the power equipment itself but, possibly, also results in very severe service reductions due to the down time associated with repair. To avoid such a condition, increasing use is being made of a diagnosis system, which may, for example, also include an optical measurement device, for early identification of defects. The diagnosis system furthermore allows a higher utilization level, making the power equipment more financially viable.
The physical configuration of the power equipment is optimized with regard to high efficiency, low eddy current losses, compact construction and good electrical isolation. For this reason, there are also no unused intermediate spaces or empty spaces in which a sensor could be accommodated without any redesign effort, especially in the active part of the power equipment. A stator winding or else a rotor winding of an electrical generator contains, for example, a large number of conductor bars that are pressed at high pressure into slots in a base body, in particular, a laminated stator core or a rotor body. This results in the compact construction that has been mentioned, without any significant intermediate spaces.
During operation, the conductor bars carry a very high electric current that may assume values up to the kA range, so that they are heated to a considerable extent. Their precise temperature, therefore, represents one of the important diagnosis information items. Due to the high potential difference between the individual conductor bars and between the conductor bars and the base body, an electrical sensor is not suitable for such a measurement task.
For this reason, the overview article xe2x80x9cFiber Sensors for Industrial Applicationsxe2x80x9d by M. Lequime, 12th International Conference on Optical Fiber Sensors, 28-31.10.1997, pp. 66-71, describes various optical measurement devices for an electrical generator, which each use at least one optical sensor for measurement value detection. This is because, in contrast to a conventional electrical measurement sensor, an optical sensor can still operate very well in the presence of a high electrical voltage (typically greater than several tens of kilovolts), a high magnetic field (up to 5 Tesla), and in a corrosive atmosphere (hydrogen or sulfur hexafluoride). In addition to detecting the temperature of the coolant that is used, inter alia, for cooling the conductor rods, the described optical measurement devices also detect the vibration spectrum. Not only a fiber-optic point sensor, which is configured for a single measurement point, but also a fiber-optic sensor network with a number of measurement points are used.
The specialist article xe2x80x9cA Temperature Optical Fiber Sensor Network: From Laboratory Feasibility to Field Trialxe2x80x9d by H. Fevrier et al., 8th Optical Fiber Sensors Conference, 29-31.01.1992, pp. 262-265, describes an optical measurement device that is in the form of a fiber-optic sensor network with effectively distributed temperature detection using a so-called Optical Time Delay Reflectometry (OTDR) technique. During a field test on a 250 MW generator, a number of optical temperature sensors were positioned within the generator housingxe2x80x94some on a nonmagnetic protective plate at ground potential and some on a coolant circuit water chamber at a high-voltage potential. However, no details are given about the precise installation precautions for the optical sensors or about the optical waveguide routing within the generator.
The specialist article xe2x80x9cIndustrial Prototype of a Fiber-Optic Sensor Network for the Thermal Monitoring of the Turbogenerator of a Nuclear Power Plantxe2x80x94Design, Qualification, and Settlementxe2x80x9d by C. Meunier et al. in Journal of Lightwave Technology, Vol. 13, No. 7 July 1995, pp. 1354-1361, discloses a further optical measurement device for temperature detection in a 900 MW turbogenerator. The fiberoptic sensor network is, in this case, based on so-called white light interferometry, which makes it possible to interrogate a number of optical sensors at the same time. The optical sensors, which are intended for water temperature measurement, are adhesively bonded onto a water connecting element, which is located on a conductor in the outlet region of the coolant line. The application point for the optical sensors is, thus, disposed in the region of the end winding of the generator winding.
Furthermore, on the Internet page:
http://www.luxtron.com/product/utility/fiber.html (as of Dec. 13, 1999), the Luxtron Corp. describes an optical sensor that is based on temperature-dependent fluorescence of a sensitive element. The sensor is particularly suitable for temperature measurement on the conductor winding of a high-voltage power transformer. However, no disclosure is given of how the temperature sensor can be applied to the conductor winding, or how the optical waveguide for supply purposes can be routed within the power transformer.
Furthermore, European Patent Application EP 0 071 561 A2 discloses an operating system to be monitored by optical waveguides. In addition, International Patent Application WO 98/31987 A1, corresponding to U.S. Pat. No. 5,892,860 to Maron et al., discloses a measurement variable being detected by an optical sensor in the form of a Faser-Bragg grating sensor. The Faser-Bragg grating sensor is, in this case, fitted to an electrical pump within a (natural oil) bore hole, and is connected to an evaluation unit on the earth""s surface.
The prior art optical measurement devices, thus, allow either only indirect measurement variable detection, for example, in the case of determining the temperature in the coolant circuit, or there are no specific details as to how the optical sensor and the supplying optical conductor for direct measurement variable detection can be disposed, for example, on the conductor to be monitored on the conductor winding to be monitored.
It is accordingly an object of the invention to provide an optical measurement device for an electrical appliance having at least one electrical conductor that is pressed into a slot, which has two slot side walls, in a base body that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that detects the measurement variable as directly as possible on the electrical conductor. In the process, the operation of the electrical appliance should be influenced as little as possible. Furthermore, no redesign of the electrical appliance shall be required to make it possible to operate the optical measurement device.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an optical measurement device for an electrical appliance having a base body with at least one slot having two slot side walls and at least one electrical conductor having a longitudinal face facing away from the two slot side walls and a plurality of conductor elements insulated from one another, the conductor pressed into the one slot, the optical measurement device including at least one optical sensor, at least one optical waveguide having a part adjacent the optical sensor and being connected to the optical sensor, the optical sensor to be interrogated by a light signal through the optical waveguide, an evaluation unit optically connected to the optical sensor, the optical sensor and the part to be disposed in a region of the slot at the longitudinal face, and at least one protective strip to be disposed at the longitudinal face.
The invention is based on the knowledge that the optical sensor and the part of the optical waveguide that is close to the sensor can be fitted on the longitudinal face in very close physical contact with the conductor, without this resulting in any detrimental effect on the operating behavior of the electrical appliance. The application point that has been identified as being particularly advantageous for the optical sensor and for the supply optical waveguide, thus, for the first time allows direct measurement variable detection on a conduction of an electrical appliance, in particular, in the form of power equipment. At the same time, such an application point does not require any redesign of the existing electrical appliance. It has been found that the solution according to the invention has major advantages in comparison to other application points on the conductor, not only with regard to the mechanical load on the optical sensor and on the supply optical waveguide, but also with regard to the possibility of redesign requirements.
The application point on the longitudinal face prevents unacceptably high mechanical loads acting on the optical sensor and on the optical waveguide during production and during operation of the electrical appliance. This is because, compared with the longitudinal face that faces away from the slot side walls, there is a considerably higher mechanical load on those contact faces of the conductor that face the slot side walls. Specifically, in most cases, the contact pressure acts, in particular, on these contact faces of the conductor. The fitting of the optical sensor and of the optical waveguide on the longitudinal face can, furthermore, be carried out very late in the manufacturing procedure, thus, furthermore assisting the aim of keeping the mechanical load on the optical sensor and on the optical waveguide as low as possible during the manufacturing process as well.
In accordance with another feature of the invention, at least one protective strip is additionally fitted on the longitudinal face. Such a configuration contributes to further reducing the mechanical load on the optical sensor and on the optical waveguide in the part close to the sensor. The force that acts on the longitudinal face when the conductor is being pressed into the slot is kept away from the optical sensor and from that part of the optical waveguide that is close to the sensor by the protective strip. The protective strip is composed of a material that is heat-resistant up to at least 180xc2x0 C., such as Capton. However, it may also be a composite material including at least one of the materials plastic, carbon fibers, and ceramic. One example of such a composite material is glass-fiber reinforced plastic (GFP) or an epoxy filled with quartz powder. The quartz powder in this case results in the mechanical behavior, in particular, the thermal behavior, of the protective strip being matched to that of the optical waveguide, which is normally manufactured from quartz glass. Furthermore, a Nomex strip can also be used for the protective strip.
In accordance with a further feature of the invention, the protective strip is two protective strips disposed laterally alongside one another and the optical sensor and the part are disposed between the two protective strips.
It is also advantageous to place the optical sensor and that part of the optical waveguide that is close to the sensor between two protective strips that are disposed alongside one another on the longitudinal face. The two protective strips are in this case disposed laterally alongside one another and each run parallel to the longitudinal face of the conductor. The optical sensor and the optical waveguide, which are referred to in the following text by the generic term xe2x80x9coptical componentsxe2x80x9d, are then located in a space between the two protective strips. Such a configuration results in a particular good protective effect for the optical components.
A similarly good protective effect is obtained with two different embodiments of the protective strip, in which the optical sensor and that part of the optical waveguide that is close to the sensor are at least partially or completely surrounded by the protective strip. In the first-mentioned case, the protective strip has, on one surface, an opening, for example, in the form of a groove or notch running in the longitudinal direction and into which the optical sensor and that part of the optical waveguide that is close to the sensor can easily be inserted. In the second-mentioned case, the optical sensor and that part of the optical waveguide that is close to the sensor are completely embedded in the protective strip. A protective strip construction that is particularly suitable for such a purpose includes two protective strip halves that can be joined together, one of which can be provided with a notch running in the longitudinal direction to hold that part of the optical waveguide that is close to the sensor.
In accordance with a further feature of the invention, the optical sensor is secured on a mount and is disposed, together with this mount, in a cutout that is additionally provided for such a purpose in the protective strip. This fixing of the optical sensor on the mount leads to improved sensor accuracy, particularly if the mount is composed of quartz glass so that it has the same thermal expansion behavior as the optical waveguide.
In a further preferred embodiment, at least that part of the optical waveguide that is close to the sensor, as well as the optical sensor, are disposed within an additional small tube, which is advantageously also composed of a material that is heat-resistant up to at least 180xc2x0 C., in particular, once again being composed of quartz glass. The small tube provides additional mechanical protection for the electrical components.
With the objects of the invention in view, there is also provided an optical measurement device for an electrical generator having a stator, a core, a stator winding, and a rotor, the core having at least one slot with two slot side walls, the stator winding having at least one electrical conductor with a longitudinal face facing the rotor and a plurality of conductor elements insulated from one another, the conductor pressed into the at least one slot, the optical measurement device including at least one optical sensor, at least one optical waveguide having a part adjacent the at least one optical sensor and being connected to the at least one optical sensor, the at least one optical sensor to be interrogated by a light signal through the at least one optical waveguide, an evaluation unit optically connected to the at least one optical sensor, the at least one optical sensor and the part to be disposed in a region of the slot at the longitudinal face, and at least one protective strip to be disposed at the longitudinal face.
In a further advantageous embodiment, the conductor is part of a stator winding, for example, of an electrical generator. It is particularly advantageous if the longitudinal face of the conductor on which the optical sensor and the optical waveguide are located faces a rotor of the electrical generator. The optical sensor and the optical waveguide are then located in the region of an air gap that is always present in such an electrical generator. The optical components can be disposed directly on the conductor at this point, without any redesign of the electrical generator. Such an application point furthermore has the additional advantage that this region of the conductor is severely loaded electrically and mechanically during operation, and direct measurement information from this region is, therefore, particularly valuable for generator diagnosis.
However, it is also possible for the conductor to be a component of a rotor winding of an electrical generator. Due to the high centrifugal forces that occur in the rotor, the slot in the rotor base body into which the conductor is once again likewise pressed is also normally provided with a clamping wedge on the side facing the stator. The conductor can now be pressed with a high pressure against the clamping wedge during operation, by virtue of centrifugal forces. With such a rotor winding, it is, therefore, better to dispose the optical sensor and that part of the optical waveguide that is close to the sensor on a longitudinal face of the conductor facing away from the stator, and also facing away from the slot side walls. The mechanical load at such a point, that is to say, in particular, facing a slot base, is then at a minimum.
In accordance with an added feature of the invention, the tube is of quartz glass.
In accordance with an additional feature of the invention, the at least one electrical conductor has an outer electrical insulation and the at least one optical sensor and the part are disposed under the outer electrical insulation. Because there may be a potential difference of up to several tens of kilovolts between the base body and the conductor, the conductor has appropriate external electrical insulation, with an appropriately high dielectric constant. To ensure that the optical sensor is now coupled as well as possible to the conductor, a configuration underneath the outer electrical insulation is particularly advantageous. This relates, in particular, to temperature measurement on the conductor.
Because the optical sensor as well as the optical waveguide are composed only of dielectric material, the configuration underneath the outer electrical insulation means that there is no deterioration in the dielectric strength, either. The outer electrical insulation may, for example, include a multi-layer winding, in particular, impregnated with an epoxy resin, consisting of an insulating tape. The optical waveguide is preferably routed in the region of the base body underneath the outer electrical insulation and, in the region of a so-called end winding, which is located outside the base body and which is used for the electrical interconnection of a number of conductor bars that are pressed into the base body, is passed through the outer electrical insulation. To keep the mechanical load as low as possible, the optical components are preferably not fitted to the longitudinal face of the conductor until immediately before the outer electrical insulation is fitted.
It is particularly advantageous for the optical sensor to be in the form of a Faser-Bragg grating sensor, which can be produced scribing a Bragg grating into the optical waveguide. The geometrical dimensions of such an advantageous Faser-Bragg grating sensor are substantially governed by the optical waveguide that is used. Because this results in the Faser-Bragg grating sensor occupying an extremely small amount of space, it is easier to mount it on the longitudinal face of the conductor. It is furthermore advantageous that there is no need to input and output an optical signal into and out of the optical waveguide, in order to detect the measurement variable. In the case of a Faser-Bragg grating sensor, the light is always routed within the optical waveguide, thus, allowing measurement variables to be detected in a particularly insensitive manner.
The optical sensor that is used can be constructed to detect various measurement variables. The configuration in the form of a fiber-optic temperature sensor is particularly simple, while at the same time also being very useful for generator diagnosis. This is because the temperature detected directly on the conductor represents important information for a diagnosis system for monitoring the state of the electrical appliance. However, the optical sensor may also be configured for detecting another measurement variable, for example, mechanical vibration or mechanical acceleration.
In accordance with yet another feature of the invention, the at least one protective strip is connected to the at least one optical waveguide.
In accordance with yet a further feature of the invention, the at least one protective strip is two protective strips and the at least one optical waveguide is between the two protective strips.
In accordance with a concomitant feature of the invention, the at least one protective strip is one protective strip and the at least one optical waveguide is in the protective strip.
The optical measurement device may also, in particular, include a number of optical sensors and a number of optical waveguides. Such a sensor network then provides information from a large number of different measurement points within the electrical appliance so that it is possible to carry out a sound diagnosis procedure relating to the state of the electrical appliance.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an optical measurement device in a pressed-in conductor bar in an electrical machine, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.